1. Field of the Invention
This invention relates to a liquid sprayer of the type comprising: a body having therein a cylinder defining a pump chamber, a discharge conduit and a passage between said chamber and said conduit, with a port forming a valve seat on the conduit side of said passage; a stem housed in said discharge conduit having an end forming a valve body capable of sealingly engaging said port; a first spring urging said stem end in engagement with said port; a tubular piston extended by a dip tube and capable of sliding within said cylinder between a minimum insertion position and a maximum insertion position and having a check valve controlling the communication between the dip tube and the pump chamber; a second spring urging said piston to the minimum insertion position thereof in said cylinder; a rocking trigger adapted to cause the sliding movement of said piston; means for mounting said trigger to said body; and means for attachment to a liquid containing receptacle.
2. Description of the Prior Art
The known sprayers of this type have certain drawbacks. One of these drawbacks (occurring particularly when the pump chamber has large dead spaces, even when the piston is in the maximum insertion position thereof in the chamber and even when the spring urging the stem is very powerful) is that, on first use, namely, when the pump chamber is full of air only, several piston strokes are required to expel such air. A further drawback is that the first and/or last amount of liquid discharged each time the piston is operated is sprayed at a low pressure and therefore is reduced to dripping or a weak jet which does not hit the target, whereby, on the one hand liquid is wasted and, on the other, it may fall where not wanted.
Further drawbacks arise with the regular attachment systems for the sprayer body to the means for coupling to a receptacle. This means usually comprises a screw cap and in the usually known models the sprayer body is attached to the screw cap with a tight press fit between the screw cap and the sprayer body, causing material fatigue.